The field of the invention relates to optoelectric data transmission systems, and to interconnection of optical subassemblies.
The use of optical fibers continues to increase in future generation communications technology. One important aspect of optical fiber technology is the interconnecting of optical fibers with optical devices such as photodetectors and semiconductor lasers. The interconnections are important for optical devices that either receive optical energy from optical fibers or devices that transmit optical energy to optical fibers. An interconnect substrate is often used to connect passive and active optical components. Presently, coupling of an optical device, interconnect substrate, and optical fibers can be a difficult task. Using manual or semi manual methods have several problems including complexity and inefficiency, thus making high volume production difficult.
In order to minimize optical alignment losses in multimode optical fiber, a placement tolerance of +/xe2x88x925 micrometers is needed. In addition, the 3 standard deviation alignment tolerances of single-mode optical fiber is less than 1 micron. Thus, there is a need for high precision alignment and placement of optical components. To achieve this alignment tolerance, active alignment and complex vision systems are often used. Yet, this alignment requirement reduces manufacturing output and yield, making optical assemblies more costly than traditional electronic packaging techniques.
By comparison, electronic packaging assemblers use pick-and-place methodology to position components for subsequent assembly processes. Components are picked from a component holder and placed on a substrate to within 25 microns of an absolute reference position. This alignment tolerance is 5 times greater than required for low-loss optical interconnects.
As previously stated the conventional method of aligning optical fibers to optical devices is active alignment. To couple a semiconductor laser to an optical fiber by active alignment, the laser is activated to emit optical energy. A coupling end of the optical fiber is then placed near a light-emitting surface of the laser to receive optical energy, and a photodetector is placed at the other end of the fiber to detect the amount of optical energy that is coupled into the fiber. The position of the laser is then manipulated around the coupling end of the fiber until the photo detector at the other end of the fiber detects maximum optical energy. An epoxy is then applied to both the laser and coupling end of the fiber to permanently maintain the optical coupling. This method of alignment as described can be complicated and may reduce manufacturing efficiency.
In this patent is described a detailed methodology to simplify optical component assembly, couple light between optical components more efficiently, increase component assembly yields, and minimize optical alignment tolerance stack up.
A method and apparatus are provided for aligning an optical array with a substrate. The method includes the steps of aligning the substrate with a set of alignment structures on an alignment fixture, transmitting a plurality of optical signals from the fixture through the substrate, and automatically aligning the optical array to the substrate using the transmitted plurality of optical signals and a pick and place machine.